I speak in precisely the way that I was taught at school

By which I assume you mean that schools actively teach non-accented pronunciation. That is a concept so out of the scope of US schools that it's hard to fathom.

I've lived in a city all my life, which means that most of the people I grew up with didn't have a very rural accent. Since working for the state, which, for whatever reason, seems to employ a lot of folks from the sticks, I amazed at the bright people who sound like they've jumped out of the pages of Lil' Abner.

I guess the point is that my reasonable lack of accent is almost solely due to non-school influence -- environment, a lot of TV, etc.